From patchwork Thu Feb 10 11:21:55 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Schoenebeck X-Patchwork-Id: 12741805 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5631CC433F5 for ; Thu, 10 Feb 2022 11:44:11 +0000 (UTC) Received: from localhost ([::1]:49642 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nI7ru-0000hK-Bn for qemu-devel@archiver.kernel.org; Thu, 10 Feb 2022 06:44:10 -0500 Received: from eggs.gnu.org ([209.51.188.92]:43378) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nI7kE-0007ez-Dm for qemu-devel@nongnu.org; Thu, 10 Feb 2022 06:36:14 -0500 Received: from lizzy.crudebyte.com ([91.194.90.13]:44165) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nI7k5-0003Vn-5R for qemu-devel@nongnu.org; Thu, 10 Feb 2022 06:36:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=lizzy; h=Cc:To:Subject:Date:From:References:In-Reply-To: Message-Id:Content-Type:Content-Transfer-Encoding:MIME-Version:Content-ID: Content-Description; bh=fOUlgj1WIfegIgJq1TPnqkVSNHErz2qLJSzUUdgRiHc=; b=H/VVi 38RnVURHDJXbsTQGCerRa9/DBWArClSajmEW4wmKbBwtz/fQ5+NWXUzcg3rLroXzNriL08Oe24Rba fT3cRgLc0CqqHP3JpfjF6hamByy4ch3ayi4HABOvwVF9kOMyb/CtLSCgi4t+Uw+NI+0xqnS3jpZTn jTDn7Xw8iP/ShwqcMeuz4hltWv6KlVWVPgPhsCiCxAaaU0Qlf3hqalnWerdovhNLDASiEI38DrOQp 6B0+Cp7XWfH7ULHB6h8757/1Z4z4A/+2Awa0X/PFMPjnZBeB43CH+G6S6MJCtXY1HZX57V8EGm51B Ux4nskNmOn9E1paqc/cYps5uogiZg==; Message-Id: In-Reply-To: References: From: Christian Schoenebeck Date: Thu, 10 Feb 2022 12:21:55 +0100 Subject: [PULL 5/5] 9pfs: Fix segfault in do_readdir_many caused by struct dirent overread To: qemu-devel@nongnu.org, Peter Maydell Cc: Greg Kurz Received-SPF: none client-ip=91.194.90.13; envelope-from=de19c79dad6a2cad54ae04ce754d47c07bf9bc93@lizzy.crudebyte.com; helo=lizzy.crudebyte.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Vitaly Chikunov `struct dirent' returned from readdir(3) could be shorter (or longer) than `sizeof(struct dirent)', thus memcpy of sizeof length will overread into unallocated page causing SIGSEGV. Example stack trace: #0 0x00005555559ebeed v9fs_co_readdir_many (/usr/bin/qemu-system-x86_64 + 0x497eed) #1 0x00005555559ec2e9 v9fs_readdir (/usr/bin/qemu-system-x86_64 + 0x4982e9) #2 0x0000555555eb7983 coroutine_trampoline (/usr/bin/qemu-system-x86_64 + 0x963983) #3 0x00007ffff73e0be0 n/a (n/a + 0x0) While fixing, provide a helper for any future `struct dirent' cloning. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/841 Cc: qemu-stable@nongnu.org Co-authored-by: Christian Schoenebeck Reviewed-by: Dmitry V. Levin Signed-off-by: Vitaly Chikunov Acked-by: Greg Kurz Reviewed-by: Christian Schoenebeck Message-Id: <20220206013419.849161-1-vt@altlinux.org> Signed-off-by: Christian Schoenebeck --- hw/9pfs/codir.c | 3 +-- include/qemu/osdep.h | 13 +++++++++++++ util/osdep.c | 21 +++++++++++++++++++++ 3 files changed, 35 insertions(+), 2 deletions(-) diff --git a/hw/9pfs/codir.c b/hw/9pfs/codir.c index 032cce04c4..c0873bde16 100644 --- a/hw/9pfs/codir.c +++ b/hw/9pfs/codir.c @@ -143,8 +143,7 @@ static int do_readdir_many(V9fsPDU *pdu, V9fsFidState *fidp, } else { e = e->next = g_malloc0(sizeof(V9fsDirEnt)); } - e->dent = g_malloc0(sizeof(struct dirent)); - memcpy(e->dent, dent, sizeof(struct dirent)); + e->dent = qemu_dirent_dup(dent); /* perform a full stat() for directory entry if requested by caller */ if (dostat) { diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index d1660d67fa..ce12f64853 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -805,6 +805,19 @@ static inline int platform_does_not_support_system(const char *command) } #endif /* !HAVE_SYSTEM_FUNCTION */ +/** + * Duplicate directory entry @dent. + * + * It is highly recommended to use this function instead of open coding + * duplication of @c dirent objects, because the actual @c struct @c dirent + * size may be bigger or shorter than @c sizeof(struct dirent) and correct + * handling is platform specific (see gitlab issue #841). + * + * @dent - original directory entry to be duplicated + * @returns duplicated directory entry which should be freed with g_free() + */ +struct dirent *qemu_dirent_dup(struct dirent *dent); + #ifdef __cplusplus } #endif diff --git a/util/osdep.c b/util/osdep.c index 42a0a4986a..67fbf22778 100644 --- a/util/osdep.c +++ b/util/osdep.c @@ -33,6 +33,7 @@ extern int madvise(char *, size_t, int); #endif +#include #include "qemu-common.h" #include "qemu/cutils.h" #include "qemu/sockets.h" @@ -615,3 +616,23 @@ writev(int fd, const struct iovec *iov, int iov_cnt) return readv_writev(fd, iov, iov_cnt, true); } #endif + +struct dirent * +qemu_dirent_dup(struct dirent *dent) +{ + size_t sz = 0; +#if defined _DIRENT_HAVE_D_RECLEN + /* Avoid use of strlen() if platform supports d_reclen. */ + sz = dent->d_reclen; +#endif + /* + * Test sz for zero even if d_reclen is available + * because some drivers may set d_reclen to zero. + */ + if (sz == 0) { + /* Fallback to the most portable way. */ + sz = offsetof(struct dirent, d_name) + + strlen(dent->d_name) + 1; + } + return g_memdup(dent, sz); +}